Radiation: what we do and do not know

Accidents at Chernobyl and Fukushima expose how little we know about radiation

As the baton of nuclear disaster is handed after 25 years from Chernobyl to Fukushima, scientists still find themselves with more questions than answers on the effects of radiation on human health.

Vitalik Dashkevich is 18, has blonde hair and sparkling hazel eyes, but beneath his chin is the scar where doctors cut a tumour from his neck before his sixteenth birthday. He is among hundreds of children and teenagers the Chernobyl Children’s Project brings on respite holidays from contaminated areas of Belarus to Britain every year.

Despite being out of school for two years and spending months in the Minsk cancer hospital, he is not against nuclear power. “The old reactors were unsafe. The new generation of reactors are safer, it couldn’t happen again,” he says.

But it has. Tragically, 25 years almost to the month after Chernobyl, history threatens to repeat itself at the stricken Fukushima Daiichi power plant in Japan, where partial meltdowns in four reactors have yet to be brought under control after eight weeks.

Described as “apocalyptic” by Germany’s chancellor Angela Merkel, Fukushima was this month updated to a level 7 event on the International Nuclear Events Scale – the highest level, which it shares only with Chernobyl. Germany, where anti-nuclear feeling has always run high, looks likely to invest in renewable energy rather than nuclear power.

It remains a highly divisive issue. Talk of radiation provokes fear and hostility despite the presence of background radiation across the planet in rocks, soils, food, the air and in our bodies, and despite the undeniable benefits of radiotherapy, X-rays, CT scans, or power. Radiation is invisible and poorly understood by the public, but even in scientific circles there is still much that is debated.

Our understanding of ionizing radiation comes mostly from the Life Span Studies of the Hiroshima and Nagasaki atomic bomb survivors. The effects of large doses of radiation, especially when received in short periods of time, are generally agreed: radiation sickness occurs at around 1 sievert (Sv, the unit of radiological dose, equivalent to 1,000 millisieverts or mSv), severe radiation sickness after 2,000 mSv, and death is likely beyond 4,000 mSv. Background radiation in Britain is 2.7 millisieverts per year, of which man-made radiation makes up around 20 per cent, mostly from medical imaging.

By comparison, the radiation levels around the Fukushima nuclear plant are in the range of 0.03 mSv to 0.5 mSv per hour indicating that, at worst, spending five hours at the plant would be about the same as a year’s background dose in Britain.

The Linear No Threshold theory (LNT) adopted by the International Commission on Radiological Protection (ICRP) holds that risk increases with radiation dose, with near-zero levels posing a near-zero risk, increasing in line with dose. So according to the models used to draw up safety codes, low levels of radiation below 1 mSv – considerably lower than the background radiation – pose a risk so small as to be statistically invisible. This is the model used by the industry and other government watchdogs such as Britain’s Health Protection Agency.

But a growing number of scientific studies claim to show the LNT theory is inaccurate and unscientific, although perhaps demonstrating the limits of our understanding of radiation, however, it is either more dangerous, or less dangerous than the LNT model represents depending on who you ask. Some even suggest a little radiation is good for you.

One problem is that we don’t understand the mechanism by which radiation affects the body. Former World Health Organisation radiation biologist Dr Keith Baverstock says: “We know that after a dose of radiation you can find chromosomal damage and cell mutations. Then there’s a big gap, and then cancer appears. But until we know how we’re on shaky ground making any claims.” With cancer already running as high as one in three people among some populations, this makes it difficult for studies to accurately identify additional cancers that may have been caused by radiation.

Some have taken the lack of coherent findings that are not contradicted by other studies as proof that radiation poses no danger below the high levels required to cause radiation sickness. The radiation hormesis theory suggests that, similar to a vaccine, small amounts of radiation stimulate the body’s natural defences, actually increasing health. Belle, Beneficial Effects of Low Level Exposures, was set up in 1990 to study such theories and gather evidence that demonstrates the hormesis effect. For example, one study of residents from an apartment block in Taiwan built with steel accidentally contaminated with radioactive cobalt-60, found that among the 10,000 residents who had lived there for nine or more years rates of cancer were much lower than the model predicted, despite the dose they had received.

However, other studies suggest that the LNT model is wrong because it fails to take into account the impact of radioactive particles absorbed by the body in food, water or air – so-called internal emitters – which potentially effect the body very differently to the strong, external radiation blast experienced by the atom bomb survivors on which the risk model is based. Independent radiological consultant Dr Ian Fairlie says even background radiation, while occurring naturally, is not benign. In fact radioactive radon gas, a by-product of natural uranium found in the earth, causes an estimated 21,000 lung cancers a year according to the US Environmental Protection Agency. Strictly, the doses of radiation received by inhaling radon gas are not sufficient to cause harm under the model used by the ICRP. Yet while radon is the accepted cause, the same model rejects the idea that low doses from caesium, strontium and plutonium fallout from Chernobyl – and now Fukushima – is high enough to cause harm.

Fairlie says: “It has everything to do with the politics of nuclear power, and nothing to do with the science. It is a case of fitting the science around the policy. We all do it to an extent, but it is important to take the most unbiased approach possible, and not cherry-pick the evidence.”

The Committee Examining Radiological Risks of Internal Emitters, set up by the government and on which Fairlie sat, concluded in 2004 that the uncertainties surrounding internal doses were so large – differences of between two and ten times predictions – as to make the model’s estimates almost useless.

In 2008, the German KiKK study (Kinderkrebs in der Umgebung von KernKraftwerken, Childhood Cancer in the Vicinity of Nuclear Power Plants) examined data stretching back 10 years and found a regular pattern of childhood leukaemias that increased with proximity to nuclear plants. Similar studies had been carried out at Sellafield in the 1980s, which discovered no less than seven cases of childhood leukaemia in one village, Seascale, four miles from the plant.

“You have to be upfront and transparent about nuclear power. The government should have stated that in the worst instance we could expect a few deaths in the local population,” Fairlie says.

But is it reasonable to single out the dangers from nuclear power when the alternatives also come with risk attached? Fly ash released by coal-burning power stations contains radioactive uranium, thorium and radium – something known since at least a 1978 study of Tennessee and Alabama coal plants found doses of up to 1.8 mSv to those living within a mile – but without sparking the same media hysteria. That’s to say nothing of the tens hundreds of thousands of deaths from air pollution the world over, and the thousands of deaths in mines – 30 a year in the US; more than 2,000 a year in China alone. Even wind turbines have led to 69 deaths since the 1970s according to Caithness Windfarms Information Forum – comparable to those killed in nuclear accidents, but having produced a fraction of the power.

Modern society needs power, and it is prepared to accept a degree of risk in generating it but, says Baverstock, our approach to risk is not rational: “People will happily do things that are high risk like smoking. People are prepared to accept risk if they feel they’re getting a benefit from it, but perhaps don’t see nuclear power sustaining the electricity grid as benefit enough.

“We must be consistent,” he warns. “How are the public to make a decision if we tell them to avoid unnecessary CT scans because of the risk they pose, while at the same time telling us that radiation of a similar level radiation from power plants is harmless?”

Part one of this debate on nuclear power is here.

 

[This article was originally published in The Big Issue, May 2011]